Kinship can refer both to the patterns of social relationships themselves, or it can refer to the study of the patterns of social relationships in one or more human cultures (i.e. kinship studies). Over its history, anthropology has developed a number of related concepts and terms in the study of kinship, such as descent, descent group, lineage, affinity/affine, consanguinity/cognate and fictive kinship. Further, even within these two broad usages of the term, there are different theoretical approaches.

Broadly, kinship patterns may be considered to include people related by both descent – i.e. social relations during development – and by marriage. Human kinship relations through marriage are commonly called "affinity" in contrast to the relationships that arise in one's group of origin, which may be called one's descent group. In some cultures, kinship relationships may be considered to extend out to people an individual has economic or political relationships with, or other forms of social connections. Within a culture, some descent groups may be considered to lead back to gods^[2] or animal ancestors (totems). This may be conceived of on a more or less literal basis.

Kinship can also refer to a principle by which individuals or groups of individuals are organized into social groups, roles, categories and genealogy by means of kinship terminologies. Family relations can be represented concretely (mother, brother, grandfather) or abstractly by degrees of relationship (kinship distance). A relationship may be relative (e.g. a father in relation to a child) or reflect an absolute (e.g. the difference between a mother and a childless woman). Degrees of relationship are not identical to heirship or legal succession. Many codes of ethics consider the bond of kinship as creating obligations between the related persons stronger than those between strangers, as in Confucian filial piety.

In a more general sense, kinship may refer to a similarity or affinity between entities on the basis of some or all of their characteristics that are under focus. This may be due to a shared ontological origin, a shared historical or cultural connection, or some other perceived shared features that connect the two entities. For example, a person studying the ontological roots of human languages (etymology) might ask whether there is kinship between the English word seven and the German word sieben. It can be used in a more diffuse sense as in, for example, the news headline "Madonna feels kinship with vilified Wallis Simpson", to imply a felt similarity or empathy between two or more entities.

In biology, "kinship" typically refers to the degree of genetic relatedness or the coefficient of relationship between individual members of a species (e.g. as in kin selection theory). It may also be used in this specific sense when applied to human relationships, in which case its meaning is closer to consanguinity or genealogy.

Basic concepts

Family types

Family is a group of people affiliated by consanguinity (by recognized birth), affinity (by marriage), or co-residence/shared consumption (see Nurture kinship). In most societies, it is the principal institution for the socialization of children. As the basic unit for raising children, Anthropologists most generally classify family organization as matrifocal (a mother and her children); conjugal (a husband, his wife, and children; also called nuclear family); avuncular (a brother, his sister, and her children); or extended family in which parents and children co-reside with other members of one parent's family.

However, producing children is not the only function of the family; in societies with a sexual division of labor, marriage, and the resulting relationship between two people, it is necessary for the formation of an economically productive household.^[3][4][5]

Terminology

 

A mention of "cȳnne" (kinsmen) in the Beowulf

Different societies classify kinship relations differently and therefore use different systems of kinship terminology – for example some languages distinguish between affinal and consanguine uncles, whereas others have only one word to refer to both a father and his brothers. Kinship terminologies include the terms of address used in different languages or communities for different relatives and the terms of reference used to identify the relationship of these relatives to ego or to each other.

Kin terminologies can be either descriptive or classificatory. When a descriptive terminology is used, a term refers to only one specific type of relationship, while a classificatory terminology groups many different types of relationships under one term. For example, the word brother in English-speaking societies indicates a son of one's same parent; thus, English-speaking societies use the word brother as a descriptive term referring to this relationship only. In many other classificatory kinship terminologies, in contrast, a person's male first cousin (whether mother's brother's son, mother's sister's son, father's brother's son, father's sister's son) may also be referred to as brothers.

The major patterns of kinship systems that are known which Lewis Henry Morgan identified through kinship terminology in his 1871 work Systems of Consanguinity and Affinity of the Human Family are:

• Iroquois kinship (also known as "bifurcate merging")
• Crow kinship (an expansion of bifurcate merging)
• Omaha kinship (also an expansion of bifurcate merging)
• Eskimo kinship (also referred to as "lineal kinship")
• Hawaiian kinship (also referred to as the "generational system")
• Sudanese kinship (also referred to as the "descriptive system")^{[citation needed]}

There is a seventh type of system only identified as distinct later:

• Dravidian kinship (the classical type of classificatory kinship, with bifurcate merging but totally distinct from Iroquois). Most Australian Aboriginal kinship is also classificatory.

The six types (Crow, Eskimo, Hawaiian, Iroquois, Omaha, Sudanese) that are not fully classificatory (Dravidian, Australian) are those identified by Murdock (1949) prior to Lounsbury's (1964) rediscovery of the linguistic principles of classificatory kin terms.

Tri-relational Kin-terms

While normal kin-terms discussed above denote a relationship between two entities (e.g. the word 'sister' denotes the relationship between the speaker or some other entity and another feminine entity who shares the parents of the former), trirelational kin-terms—also known as triangular, triadic, ternary, and shared kin-terms—denote a relationship between three distinct entities. These occur commonly in Australian Aboriginal languages with the context of Australian Aboriginal kinship.

In Bininj Kunwok,^[6] for example, the bi-relational kin-term nakurrng is differentiated from its tri-relational counterpart by the position of the possessive pronoun ke. When nakurrng is anchored to the addressee with ke in the second position, it simply means 'brother' (which includes a broader set of relations than in English). When the ke is fronted, however, the term nakurrng now incorporates the male speaker as a propositus (P i.e. point of reference for a kin-relation) and encapsulates the entire relationship as follows:

• The person (Referent) who is your (Addressee) maternal uncle and who is my (Speaker) nephew by virtue of you being my grandchild.

Kin-based Group Terms and Pronouns

Many Australian languages also have elaborate systems of referential terms for denoting groups of people based on their relationship to one another (not just their relationship to the speaker or an external propositus like 'grandparents'). For example, in Kuuk Thaayorre, a maternal grandfather and his sister are referred to as paanth ngan-ngethe and addressed with the vocative ngethin.^[7] In Bardi, a father and his sister are irrmoorrgooloo; a man's wife and his children are aalamalarr.

In Murrinh-patha, nonsingular pronouns are differentiated not only by the gender makeup of the group, but also by the members' interrelation. If the members are in a sibling-like relation, a third pronoun (SIB) will be chosen distinct from the Masculine (MASC) and Feminine/Neuter (FEM).^[8]

Descent

Descent rules

In many societies where kinship connections are important, there are rules, though they may be expressed or be taken for granted. There are four main headings that anthropologists use to categorize rules of descent. They are bilateral, unilineal, ambilineal and double descent.^[9]

• Bilateral descent or two-sided descent affiliates an individual more or less equally with relatives on his father's and mother's sides. A good example is the Yakurr of the Crossriver state of Nigeria.
• Unilineal rules affiliates an individual through the descent of one sex only, that is, either through males or through females. They are subdivided into two: patrilineal (male) and matrilineal (female). Most societies are patrilineal. Examples of a matrilineal system of descent are the Nyakyusa of Tanzania and the Nair of India. Many societies that practise a matrilineal system often have a matrilocal residence but men still exercise significant authority.
• Ambilineal (or Cognatic) rule affiliates an individual with kinsmen through the father's or mother's line. Some people in societies that practise this system affiliate with a group of relatives through their fathers and others through their mothers. The individual can choose which side he wants to affiliate to. The Samoans of the South Pacific are an excellent example of an ambilineal society. The core members of the Samoan descent group can live together in the same compound.
• Double descent (or double unilineal descent) refers to societies in which both the patrilineal and matrilineal descent group are recognized. In these societies an individual affiliates for some purposes with a group of patrilineal kinsmen and for other purposes with a group of matrilineal kinsmen. Individuals in societies that practice this are recognized as a part of multiple descent groups, usually at least two. The most widely known case of double descent is the Afikpo of Imo state in Nigeria. Although patrilineage is considered an important method of organization, the Afikpo considers matrilineal ties to be more important.

Descent groups

A descent group is a social group whose members talk about common ancestry. A unilineal society is one in which the descent of an individual is reckoned either from the mother's or the father's line of descent. Matrilineal descent is based on relationship to females of the family line. A child would not be recognized with their father's family in these societies, but would be seen as a member of their mother's family's line.^[10] Simply put, individuals belong to their mother's descent group. Matrilineal descent includes the mother's brother, who in some societies may pass along inheritance to the sister's children or succession to a sister's son. Conversely, with patrilineal descent, individuals belong to their father's descent group. Children are recognized as members of their father's family, and descent is based on relationship to males of the family line.^[10] Societies with the Iroquois kinship system, are typically unilineal, while the Iroquois proper are specifically matrilineal.

In a society which reckons descent bilaterally (bilineal), descent is reckoned through both father and mother, without unilineal descent groups. Societies with the Eskimo kinship system, like the Inuit, Yupik, and most Western societies, are typically bilateral. The egocentric kindred group is also typical of bilateral societies. Additionally, the Batek people of Malaysia recognize kinship ties through both parents' family lines, and kinship terms indicate that neither parent nor their families are of more or less importance than the other.^[11]

Some societies reckon descent patrilineally for some purposes, and matrilineally for others. This arrangement is sometimes called double descent. For instance, certain property and titles may be inherited through the male line, and others through the female line.

Societies can also consider descent to be ambilineal (such as Hawaiian kinship) where offspring determine their lineage through the matrilineal line or the patrilineal line.

Lineages, clans, phratries, moieties, and matrimonial sides

A lineage is a unilineal descent group that can demonstrate their common descent from a known apical ancestor. Unilineal lineages can be matrilineal or patrilineal, depending on whether they are traced through mothers or fathers, respectively. Whether matrilineal or patrilineal descent is considered most significant differs from culture to culture.

A clan is generally a descent group claiming common descent from an apical ancestor. Often, the details of parentage are not important elements of the clan tradition. Non-human apical ancestors are called totems. Examples of clans are found in Chechen, Chinese, Irish, Japanese, Polish, Scottish, Tlingit, and Somali societies.

A phratry is a descent group composed of three or more clans each of whose apical ancestors are descended from a further common ancestor.

If a society is divided into exactly two descent groups, each is called a moiety, after the French word for half. If the two halves are each obliged to marry out, and into the other, these are called matrimonial moieties. Houseman and White (1998b, bibliography) have discovered numerous societies where kinship network analysis shows that two halves marry one another, similar to matrimonial moieties, except that the two halves—which they call matrimonial sides^[12]—are neither named nor descent groups, although the egocentric kinship terms may be consistent with the pattern of sidedness, whereas the sidedness is culturally evident but imperfect.^[13]

The word deme refers to an endogamous local population that does not have unilineal descent.^[14] Thus, a deme is a local endogamous community without internal segmentation into clans.

House societies

In some societies kinship and political relations are organized around membership in corporately organized dwellings rather than around descent groups or lineages, as in the "House of Windsor". The concept of a house society was originally proposed by Claude Lévi-Strauss who called them "sociétés à maison".^[15][16] The concept has been applied to understand the organization of societies from Mesoamerica and the Moluccas to North Africa and medieval Europe.^[17][18] Lévi-Strauss introduced the concept as an alternative to 'corporate kinship group' among the cognatic kinship groups of the Pacific region. The socially significant groupings within these societies have variable membership because kinship is reckoned bilaterally (through both father's and mother's kin) and comes together for only short periods. Property, genealogy and residence are not the basis for the group's existence.^[19]

Marriage (affinity)

Marriage is a socially or ritually recognized union or legal contract between spouses that establishes rights and obligations between them, between them and their children, and between them and their in-laws.^[20] The definition of marriage varies according to different cultures, but it is principally an institution in which interpersonal relationships, usually intimate and sexual, are acknowledged. When defined broadly, marriage is considered a cultural universal. A broad definition of marriage includes those that are monogamous, polygamous, same-sex and temporary.

The act of marriage usually creates normative or legal obligations between the individuals involved, and any offspring they may produce. Marriage may result, for example, in "a union between a man and a woman such that children born to the woman are the recognized legitimate offspring of both partners."^[21] Edmund Leach argued that no one definition of marriage applied to all cultures, but offered a list of ten rights frequently associated with marriage, including sexual monopoly and rights with respect to children (with specific rights differing across cultures).^[22]

There is wide cross-cultural variation in the social rules governing the selection of a partner for marriage. In many societies, the choice of partner is limited to suitable persons from specific social groups. In some societies the rule is that a partner is selected from an individual's own social group – endogamy, this is the case in many class and caste based societies. But in other societies a partner must be chosen from a different group than one's own – exogamy, this is the case in many societies practicing totemic religion where society is divided into several exogamous totemic clans, such as most Aboriginal Australian societies. Marriages between parents and children, or between full siblings, with few exceptions,^{[23][24][25][26][27][28][29]} have been considered incest and forbidden. However, marriages between more distant relatives have been much more common, with one estimate being that 80% of all marriages in history have been between second cousins or closer.^[30]

Alliance (marital exchange systems)

An Alliance Marriage is not a legal right as to an "adoption" into blood family, but works as a systemic forms of preferential marriage with wider social implications in terms of economic and political organization rather instead. In a wide array of lineage-based societies with a classificatory kinship system, potential spouses are sought from a specific class of relatives as determined by a prescriptive marriage rule. Insofar as regular marriages following prescriptive rules occur, lineages are linked together in fixed relationships; these ties between lineages may form political alliances in kinship dominated societies.^[31] French structural anthropologist Claude Lévi-Strauss developed the alliance theory to account for the "elementary" kinship structures created by the limited number of prescriptive marriage rules possible.^[32]

Claude Lévi-Strauss argued in The Elementary Structures of Kinship (1949), that the incest taboo necessitated the exchange of women between kinship groups. Levi-Strauss thus shifted the emphasis from descent groups to the stable structures or relations between groups that preferential and prescriptive marriage rules created.^[33]